1. Field of the Invention
This invention relates to a data card having a substrate and a data surface region and more particularly related to a data card having non-magnetic substrate and data surface region. In the preferred embodiment, the non-magnetic substrate may be a glass substrate or a glass-ceramic substrate and the data surface region comprises a magnetic storage medium.
2. Description of Prior Art
Digital data is stored in many forms. One data storage device uses spinning disks having a magnetic surface containing the digital data. The disks typically spin at a high rate of speed with the various tracks of data accessed by a radially movable data head.
Rotating magnetic memory storage devices generally include two elements namely, a rigid substance having a coating of magnetic media formed on at least one surface thereof. Aluminum alloys have been conventionally used as a substrate material for magnetic memory disks. The present trend is towards smaller disk drives driven by drive motors having less torque as such, it has become necessary to develop thin light-weight rugged disks to replace the standard metal disks formed of an aluminum alloy having a cooling of magnetic media formed thereon.
Several alternatives are known in the art for replacing a standard aluminum alloy metal disk. These alternatives include glass substrates having specifically chemically treated surfaces. Also, glass-ceramic substrates have been developed. The glass-ceramic substrate composition in crystalline phase are controlled to develop specific characteristics of the glass-ceramic which enabling use of the glass-ceramic as a rigid substrate. Glass-ceramic substrate materials may have a polished surface to enhance the lubricity, optimized thermal expansion coefficients and be free of silica, such as quartz. The known glass-ceramic substrate materials are selected to have a bulk thermal expansion which is similar to that for known rigid metal substrates used for magnetic memory disks.
For example, U.S. Pat. No. 5,744,208 discloses a glass-ceramics containing lithium disilicate in tridymite. U.S. Pat. No. 5,789,056 discloses a thin film magnetic disk having a substrate made of glass or comparable rigid material.
Typical magnetic disks utilizing a glass substrate are disclosed in U.S. Pat. Nos. 6,048,466; 5,900,324; 5,824,427; 5,789,056; 5,766,727; 5,744,208; 5,569,518; 5,378,548; and 5,037,515.
It is also known in the art to provide texturing in a predetermined pattern on a substrate the adhesion of magnetic layers to the surface of a disk substrate. Typical texturing techniques and patterns are disclosed in U.S. Pat. Nos. 5,748,421; 5,725,625; 5,626,970; 5,496,606 and 4,996,622.
It is also known in the art to utilize materials other than aluminum alloy or glass for disk substrates. U.S. Pat. No. 5,492,745 discloses disks wherein a non-magnetic substrate can be formed of a metal substrate, glass substrate, ceramic substrate or a resin substrate. Other material such as carbon substrate and s: substrate have been used as disk substrate.
U.S. Pat. Nos. 5,736,262 and 5,352,501 also disclose use of non-magnetic substrates which are textured and/or processed to enhance performance of magnetic recording mediums in formed thereon.
Another type of data storage device is the credit card having a magnet stripe along one surface. However, such cards have limited storage capacity because of the nature of the magnetic stripe and the method of recording data onto the magnetic stripe.